Yes, Anna Kournikova can relate

Some saw her as a curious choice to help replace outgoing trainer Jillian Michaels when Season 12 of "The Biggest Loser" returned to Tuesdays on NBC. But the 30-year-old says she has plenty in common with the morbidly obese contestants on the weight-loss reality show.

"I know what it's like to be judged, dissected, picked apart for all of my life," said the Russian-born tennis player who was arguably more famous for her willowy blond looks than for her court prowess. "It was so painful. I was just a kid at the time. I was being judged over here for being too pretty, or over there for not looking good enough. And God forbid I gained a pound. I heard about it. And then I was being criticized for not being a good enough tennis player and yet I knew — I knew — I was giving it everything I had."

The hyper-attention over her physical appearance — which made her one of the most sought-after celebrity images online three years in a row — triggered painful feelings of unworthiness, Kournikova said. Her personal battle with self-image taught her to quiet her inner critic — a lesson she's poised to help this season's contestants learn.

"At the end of the day, we know it's not just about calories and exercise," Kournikova said, taking a break from shooting and folding herself into one of the chairs in the living room set at the ranch. "The challenge here is how do you change your life? If you don't change who you are on the inside, the changes on the outside won't last. A lot of these people have just lost their sparkle for life and I have to help them figure out how to get it back."

Like many reality shows last week, "The Biggest Loser" got off to a rough start. Ratings for the premiere in the advertiser-coveted 18-49 demographic dropped more than 20% compared with the previous season. (ABC's"Dancing With the Stars" fell more than a third compared with its opener last fall.)

Kournikova joins "Biggest Loser" veteran Bob Harper and another new trainer, Dolvett Quince, who counts Justin Bieber among his personal clients. The training shake-up comes as the series attempts to shift the focus away from calories and workouts to overall health and wellness, said executive producer Todd Lubin.

He said he'd been mulling over possible roles for Kournikova after she proved popular with viewers during a guest stint several seasons ago. At that time, she led them through drills and a made-up game on the tennis court to encourage contestants to keep workouts fresh and less like, well, work.

"That was an important message," Lubin said. "Working out doesn't have to happen in a gym, it can be at a park, playing with your family, and that's what we want to get at more. How to incorporate health and fitness into your everyday life."

Harper said Kournikova brings with her the spirit of a champion and the drive that comes with being a professional athlete. "When you are a pro, you don't just get to say, 'I don't feel like working out today.' You don't have that luxury. Anna will be able to help [the contestants] find that ability, that inner strength, to fight through whatever is standing in their way."

Much like she did in her earlier appearance on the show, Kournikova said she wants to impart a love of fitness and healthy eating to the competitors as well. "Taking care of yourself, and watching what you eat isn't a punishment," she said. "You don't want to go to the gym? Don't go. But do something else."

She said being part of a team will also play to her strength. Although she peaked at No. 8 in singles on the women's tennis tour and never won a singles title, she excelled in doubles — reaching that coveted No. 1 slot and winning two Grand Slam titles.

"I'm very proud of that," she said. "I'm also very proud of reaching [No. 8], not many people get to say that. For me, it was an achievement."

Wearing a powder blue workout jacket and black workout pants, Kournikova said she's well aware that some people are critical of her new role. But she long ago stopped caring what anyone else thinks.

That disregard for judgment is something she wants to pass on to contestants so that they will be able to withstand the pressures of everyday life once they leave the protected environment of the show.

"If you lose at tennis, it only means the other opponent was better on that day," she said. "It doesn't mean you're a bad person, or you're not worthy. You have to have that sense of self, and give yourself the gift of saying, 'I don't care what anyone else thinks. Did I try my hardest? Did I do my best? Then I only care about what I think.'"